To match impedance means to take a group of speakers (usually more than three pairs) and forcing the combined impedance of the speakers to maintain an even 8 ohm level (or another number if required). Impedance means ‘the resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.’
On average, most home speakers have an impedance of 8 ohms. An Ohm unit measures the level of resistance, and the resistance in a speaker varies based on the frequency it is using. A stereo receiver can operate speakers with total impedance of 4 ohms or more, depending on the quality of the receiver.
By impedance matching the math is taken care of for you and gives your amplifier a steady 8 Ohm load. Impedance matching can be easily achieved by adding a speaker selector or impedance matching volume controls to your new sound system.
There’s a formula you can use to calculate the total impedance of your system when adding your speakers together in a parallel fashion (meaning adding + to +, and – to -). Every time you add parallel sets of speakers to a system, your impedance drops.
Here are some examples of common numbers:
- 2 – 8 ohm speakers together in parallel = 4 ohms
- 3 – 8 ohm speakers together in parallel = 2.67 ohms
- 4 – 8 ohm speakers together in parallel = 2 ohms
For a parallel circuit, the total Impedance (r) is given by the inverse of the sum of the inverses as illustrated by this formula:
Therefore, by ‘impedance matching’, the math is taken care of for you and gives your amplifier a steady 8 ohm load which is ideal for your amplifier (and simpler for those of us who see only hieroglyphics when we look at that formula). Impedance matching can be easily achieved by adding a speaker selector or impedance matching volume controls to your new sound system.
To illustrate, if you have an HD650 speakers, your ideal impedance matching should ideally be set at 8ohms. The 4 ohms setting is for knowledgable technicians with particular circuity needs. Note that this article refers to the process of “needing” impedance matching and what’s going on for whole house audio.
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